Various arrangements have heretofore been used for securing screws to screw driver bits. Examples of such arrangements are found in the U.S. Pat. Nos. 2,775,913 issued Jan. 1, 1957; and 2,729,998 issued Jan. 10, 1956 both to J. J. Deliso which disclose self-gripping tools having resilient shank portions sprung apart. The shank portions are insertable in the screw socket and expand to grip the interior walls of the socket whereby the screw is held releasably to the tool. The U.S. Pat. No. 1,647,343 issued Nov. 1, 1927 to B. J. Catron discloses a related tool with resilient prongs insertable in the kerf of a screw for removing or inserting the screw.
The U.S. Pat. No. 3,900,057 issued Aug. 19, 1975 to Benitz discloses an expandable bit screw holding screwdriver having a two piece longitudinally split shank which terminates at its forward ends in a dovetailed expandable bit. The bit comprises two driving tips wedge-shaped in cross section. The bit is expandable laterally by wedging together the tips using a forwardly movable sleeve encircling the shank.
The U.S. Pat. No. 4,078,596 issued Mar. 14, 1978 to E. Benitz discloses an expandable bit screw holding driver having a slide mechanism that is caused to rotate on a pair of shank elements. The slide moves the shank elements between their two positions which thicken and thin the screw driver blade. The U.S. Pat. No. 2,445,383 issued July 20, 1948 to G. W. Barlow discloses a screw driver having a two part expanding bit of the type shown by the Benitz patent.
The U.S. Pat. 2,739,629 issued Mar. 278, 1956 to J. M. Neil discloses a screw holding screw driver employing a bifurcated bit with a holding member rotatable therein.
The U.S. Pat. No. 4,338,835 issued July 13, 1982 to L. Simons discloses a fastener with ball-shaped socket receiving a complementary shaped driving head suitable for driving in a misaligned condition.